The objectives of this program/project can be summarized as follows: 1. To undertake a multidisciplinary study to elucidate the mechanisms of carcinogenesis of the mammary gland in the rat. 2. To study the biochemical mechanism of the action of three major hormones, prolactin, estrogen and progesterone, on the mammary gland during normal physiological processes and during the process of carcinogenesis. 3. To elucidate the morphogenetic and host factors which contribute to the development of breast cancer. 4. To carry out biochemical studies to elucidate the nature of hormone dependency of breast cancer in humans. 5. To study serum and tissue sialyltransferase in patients with breast cancer. 6. To study the hormonal control of lactose synthetase in mammary gland and mammary tumors. 7. To study estrogen metabolism in women with breast cancer and investigate the possible sources and disposition of extragonadal estrogens.